OS 10.5 - Boot Camp Problem...

Just having some issues with my MBP.
I did have boot camp on it running XP but have taken that off put parallels on instead. Since this when I turn on my computer I have to hold down alt to avoid going to a black screen saying Please insert bootable media then press any key!

How did you remove the Boot Camp partition? The proper way was to use the Boot Camp assistant from OS X and select "restore" from the create menu. That will remove Windows, the BC partition, and the Win boot loader.

You can choose the default startup for your Mac by going to System Preferences, Startup Disk, and selecting your Macintosh HD.